The present invention relates to a diagnosis supporting device for generating an image signal of an image of a subject used in a diagnosis of living tissue.
Irradiation of light at a specific wavelength excites living tissue, which causes a living tissue to emit fluorescence. Further, intensity of fluorescence emitted from abnormal living tissue that is suffering from a lesion such as a tumor or cancer is smaller than that emitted from normal living tissue.
Japanese Patent Laid-open publication No. 2000-023903 discloses a diagnosis supporting device that finds abnormality of an inner wall of a body cavity (a body cavity wall) such as gullet or stomach and specifies the position of the abnormality based on such a principle.
The diagnosis supporting device disclosed in the publication operates together with an existing video endoscope system that electronically captures images guided by an endoscope to display the images on a monitor.
The diagnosis supporting device is provided with a probe consisting of a number of optical fibers bundled up, a light source for alternatively supplying visible light and excitation light to the proximal end surface of the probe and an image processing circuit for providing images captured by the video endoscope system with a predetermined processing to output the processed image signals on a monitor.
When the diagnosis supporting device is used, the distal end of the video endoscope is inserted into a body cavity and then, the probe is led through a forceps channel of the video endoscope so that the tip end the probe is exposed in the body cavity. Visible light and excitation light alternatively illuminate a body cavity through the probe, and the illuminated body cavity is captured by a camera mounted on the distal end of the video endoscope.
Then, an illuminating/processing device of the video endoscope system outputs an image signal of an image when body cavity wall is illuminated by visible light (a reference image signal) and an image signal of an image when excited body cavity wall emits fluorescence (a fluorescent image signal).
The image processing circuit executes the following processes whenever one set of a reference image signal and a fluorescent image signal are acquired. That is, the image processing circuit extracts the maximum brightness levels and the minimum brightness levels from all pixels of the reference image signal and the fluorescence image signal, respectively.
Next, the image processing circuit standardizes the reference image signal and the fluorescence image signal by converting a value of a pixel having the maximum brightness level into a predetermined maximum gradation, a value of a pixel having the minimum brightness level into a predetermined minimum gradation and values of other pixels having intermediate brightness levels into corresponding gradations.
Next, the image processing circuit calculates difference between gradations of the standardized reference image signal and the standardized fluorescent image signal at the same coordinate (difference obtained by subtracting gradation at the predetermined coordinate in the standardized fluorescent image signal from gradation at the same coordinate in the standardized reference image signal) for every coordinate. Then, the image processing circuit creates a new binary image signal. A coordinate in the binary image signal corresponds to coordinates in each of the reference image signal and the fluorescent image signal. When a difference at a predetermined coordinate is equal to or larger than a predetermined threshold value, the value at the same coordinate in the binary image signal becomes “1”. On the other hand, when a difference at a predetermined coordinate is smaller than the threshold value, the value at the same coordinate in the binary image signal becomes “0”.
Next, the image processing circuit converts the reference image signal to a monochromatic RGB image signal and then creates a new RGB image signal (an observation image signal) by converting monochromatic pixels in the monochromatic RGB image signal whose coordinates are coincident with coordinates exhibiting value “1” in the binary image signal into red pixels.
The image processing circuit generates observation image signals according to the above-described processes, storing them into a buffer sequentially. Then, the image processing circuit reads an observation image signal recorded in the buffer to convert it into a NTSC video signal or a PAL video signal as an output signal to a monitor.
Therefore, an operator who performs an operation on a subject with using the diagnosis supporting device can specify an outline and unevenness of body cavity wall by a monochrome part in the observation image signal displayed on the monitor.
Further, the operator can specify maculate red parts and/or block red parts as an agmina of living tissue that emits relatively low fluorescence, i.e., parts that have high risk to be suffering from a lesion such as a tumor or cancer.
However, since the conventional diagnosis supporting device executes the above described complicated processes, the processing speed to generate the observation image signal and to record it into the buffer becomes relatively slow (10 frames per second). Therefore, there is the following inconvenience.
When a taking area of a video endoscope changes while body cavity wall is observed, the processing speed may be insufficient for change of the taking area.
For example, when the video endoscope cannot focus on body cavity wall or when image signal is overexposed because the tip end of the endoscope is too close to the body cavity wall, contrast of a monochromatic part in an observation image signal (a reference image signal) may extremely deteriorate. In such a case, since an outline and unevenness of body cavity wall become uncertain, an operator cannot specify which part in the body cavity wall is indicated by a red part in the observation image signal, which disturbs a diagnosis of living tissue.
At this moment, when the operator moves the tip of the video endoscope to focus on the body cavity wall, indication of observation image signals does not catch up with movement. As a result, the operator loses sight of an attention part, which causes operation delay.